Posted
by
samzenpus
on Thursday August 21, 2014 @04:30AM
from the new-way-of-thinking dept.

StartsWithABang writes It's the holy grail of modern particle physics: discovering the first smoking-gun, direct evidence for physics beyond the Standard Model. Sure, there are unanswered questions and unsolved puzzles, ranging from dark matter to the hierarchy problem to the strong-CP problem, but there's no experimental result clubbing us over the head that can't be explained with standard particle physics. That is, the physics of the Standard Model in the framework of quantum field theory. Or is there? Take a look at the evidence from the muon's magnetic moment, and see what might be the future of physics.

Headline ending with a question mark? Check.Big image that insists on occupying the whole screen! Check.Self-promoting claim of being the first, when there was evidence of something not being quite right with the Standard Model as early as the 90s? (I'm no physicist, but I read it on Slashdot)And finally, there is no new data. They are setting up an experiment, which will not bear fruit for years.

I'm a bit biased, but consider finding non-zero neutrino mass (via neutrino oscillations) as the first "beyond the standard model" evidence. Slashdot carried that story in its infancy, way back in 1998.

Also worth pointing out that TFA is talking about an experiment in construction that hopes to push the g-2 result past 5 sigma. It's not there yet, although 4.something sigma is still pretty darn good. Just 14 years late to the party.

The flaw is your visualizing a universe and imagining something inside exploding, rather than nothing exploding into something. For the most part, the human mind can't understand that shit, it's all jabberwocky

As someone who has not been involved in neutrino physics (at least until very recently) I'd agree that neutrino oscillations are the first physics discovered that is beyond the Standard Model. In addition even if the g-2 experiment gives a 5 sigma discrepancy it tells you very little about what any possible new physics - to do that you have to produce the new particles directly and study them.

The corrections to the muon g-2 experiment are now so high order that they involve QCD loops. These are non-perturbative and incredibly hard to calculate correctly so all a 5 sigma discrepancy may mean is that the theorists have got the calculation wrong. Indeed this has happened before with a 3 sigma g-2 'signal' going away after an error in the theory calculation was found by the student of one of my departmental colleagues.

If I show my bias then I would say that the best chance of new physics is the new LHC run starting in March 2015 where we have almost twice the energy of the previous run and higher luminosity. This should at least double the reach of the LHC for new physics over the next 3 years. After this run any sensitivity gains to new physics will come from increasing luminosity and so take far longer to achieve, perhaps giving one more doubling of the reach but over the next ~15 years and with a lot of work involved since the high luminosity LHC upgrade has incredible background rates!

I agree with your interpretation -- this very well may just mean that the QCD part is hard and the theorists didn't correctly estimate systematic errors from it. However, there's quite a push in the lattice community to actually calculate the messy nonperturbative parts, so there's hope that this will be sorted out from the theory side alongside the new Fermilab experiment.

You are an awesome person. What you do is awesome. Your attitude is awesome. You and others like you are some of the most important people in the world.

I would also like to thank you for all of the years that you have spent on Slashdot sharing information freely with us. There are others like you here, such as boristhespider, who share such incredibly amazing information.

I want to thank you sir. You have made my world a better place. Have a great

I'm a bit biased, but consider finding non-zero neutrino mass (via neutrino oscillations) as the first "beyond the standard model" evidence. Slashdot carried that story in its infancy, way back in 1998.

There's nothing in the standard model that rules out a neutrino mass: the other leptons have mass and it was only observational evidence that placed an upper bound on the mass of the neutrino. In fact, it's the standard model that predicted neutrino flavor oscillations would occur between massive neutrinos;

I admit not having read the clickbait (this is/. after all), but I presume that the real story behind it is that an experiment to measure the muon magnetic moment has recently moved [sciencemag.org] from Brookhaven to Fermilab to get access to more energetic muons. They're hoping to start measuring data in 2.5 years.

"This is/. after all" was intended to refer to "I admit not having read", but now that you point it out I suppose it is fair to say that most of the stuff posted is clickbait. I couldn't say in general whether that's because it's submitted by the authors of the links or because submitters can't be bothered to track back to the less sensational source.

Because the summary isn't a summary, it's an introduction that just ends in questions and begs you to click through to find out the answers."I thought it was just a steaming pile of turd ice-cream. What I saw next blew my mind!"

I'm not a physicist, but I do find this kind of stuff interesting enough to know that the headline is a big deal, but now I see that firstly, its another Starts With A Bang advertisement and secondly, the headline end with a question mark, so without reading the article, the answer is going to be no, there's no evidence..
*sigh*

so without reading the article, the answer is going to be no, there's no evidence

...Except for that pesky 4+ sigma deviation between the expected and measured value of g for a muon (and a brief mention of a new Fermilab experiment to push that to 7 sigma). Other than that, nope, no evidence at all.

Nothing to see here (if you have no soul whatsoever), move along (and let the real scientists do their thing so you can have your hoverboards and replicators 50 years from now).;)

I do have a question for the serious participants in this discussion, however... Since the Muon counts as 40,000 (200^2) times more sensitive to unexpected effects than the electron, why not work with the Tau instead, which should have a whopping 1.2e7 times more sensitivity?

so without reading the article, the answer is going to be no, there's no evidence...Except for that pesky 4+ sigma deviation between the expected and measured value of g for a muon (and a brief mention of a new Fermilab experiment to push that to 7 sigma). Other than that, nope, no evidence at all.

Well, yeah okay there's that. But as others have said, that's not new information. I should have said there's no new evidence.

The point of my moan is that this is yet another puff piece from StartsWithABang that frames itself as "Holy shit! Earth shattering breakthrough occurs!" when it actually hasn't. I find that annoying and something that seems to be happening more and more lately.

It is very sexy to posit PBTSM. And those physicists working in SUSY have seen their world continue to close in as the acceptable SUSY parameter space continues to shrink so there is a vested interest in keeping hope alive.

Just as Diract started out with a g of 2 and then QED improved on that and others further, I find it far more likely someone finds a higher order correction which has been overlooked than PBTSM.

I am a particle physicist, and I have worked directly on this problem. The uncertainty in the hadronic contributions to the vacuum polarization and light-by-light scattering are large enough that the supposed BSM signal is not significant.

That is, you can do nice high-order paper-and-pencil calculations of Feynman diagrams when the particles involved are electrons and muons, but there are important cases where the particles contributing to this effect are composite: hadrons (which are made of quarks). Since you cannot do calculations on hadrons without considering how the hadron is composed of quarks, you can't avoid getting into strongly coupled quantum chromodynamics (QCD). See here for further discussion: Hadronic Light-by-Light [washington.edu].

That means you can't do your calculation on paper, you have to use a supercomputer and something called lattice QCD. Unfortunately, it's easier to crank out a thousand crappy model calculations of BSM that is supposedly showing up than to properly fund studies of the theory uncertainties. As a result, the precision of the theory values are not good enough to establish whether the muon magnetic moment is consistent with the Standard Model or not.

That said, it's still an interesting place to look, and somebody will work out all the uncertainties eventually. In a few years, there might be something to talk about seriously.

Actually, the good news is that the experiment is definitely happening! They moved the ring to Fermilab last year and are busy setting it up to run. You can read more about it here: Muon g-2 at Fermilab [fnal.gov]. They even have a Facebook page [facebook.com].

The SM doesn't specify what the neutrino masses are; they're free parameters just like the quark masses. Some people might be surprised that they're nonzero, but I'm not one of them. Personally, I think some of those some people are feigning surprise so they can pretend nonzero neutrino masses count as BSM, which is a bit silly.

Actually that's not correct. The SM specified neutrino masses as zero just as it does the photon and gluon masses...or would you argue that those are free parameters as well? However I'll grant that this is not exactly a major change which is why I asked specifically about neutrino oscillations. This introduces 4 entirely new free parameters which were never included in the SM and while oscillations require that neutrinos have a mass the reverse is not true i.e. even if you give neutrinos a mass they do not

So does that mean that "Oh, really?" could also have been answered "yes", thereby disproving the statement that any headline question can be answered with "no"; or is the "no" denying the truth of the original assertion.

Gravity is not outside the 'standard model'. The 'standard model' is mostly how we interpret the world with quantization and speed of light limit. The speed of light limit says that we can't observe ANYTHING---we can only measure fields. And quantization says that those fields are granularized into quanta (since if they weren't, energy could go infinite). That's pretty much all for the standard model.

From there, we can make precise measurements of field properties and see how those properties evolve (kind o

Why do physicists insist on treating gravity as a force? Since Einstein, we know gravity is the curvature of space-time. It may be represented as a force in calculations but in reality there is no force.

If gravity is not a force then do we really have a hierarchy problem? For eg. shouldn't Newton's constant, G, be some kind of average curvature of space-time between two bodies and be calculable from this curvature?

Obviously, if this is the case, G has nothing to do with Fermi's constant and we should not co

Because it is a force? A force is anything which transfers momentum and energy around. Which gravity does.

Moreover, what seems so obvious to you that gravity is the curvature of space time? What does that mean? Because it is in no way obvious. For example, if gravity is spacetime curvature, then it doesn't really pull on things in 4D spacetime since we've already defined it away. So why do things appear to move down gravitational wells? Are they elastically colliding with a sheet of space time? Why aren't t

Gravity can be formulated as a gauge theory, like the other forces in Standard Model. It's just a different mathematical representation of General Relativity, and it also captures the gravity-as-curvature idea quite neatly. You don't see it that often because the math gets a little tricky, unless you use something like Geometric Algebra [cam.ac.uk], which made it easy enough for Master's courses.

It is confusing isn't it? Again and again someone demonstrates gravity with a sheet and a ball, and again and again there is someone looking for or talking about the 'graviton'.

Another one: The presenter starts off with an illustration of space and time being -the same thing: "space-time". But then goes on to explain space only, or time only, or both but each in their own silo.

My approach to understanding this has been to watch every documentary I can, distill the common, repeated 'truths' and extrapolat

Since Einstein, we know gravity is the curvature of space-time. It may be represented as a force in calculations but in reality there is no force.

How about I turn that around and say that Einstein showed gravity can be modelled by the curvature of space-time but in reality it is a force? The fact of the matter is that, at a fundamental level, we have no clue what gravity is. However you can represent it very well by a spin-2, mass-less particle which couples to a particle's 4-momentum (the caveat being that you cannot make this theory work without an energy cut-off at some scale for which there is no justification). Until we solve quantum gravity we simply do not know what gravity really is but, if I were to bet, I suspect the latter is closer to the truth but needs some correction for the quantum structure of space-time which is something we have no clue about.

If gravity is not a force then do we really have a hierarchy problem?

Yes, and if anything it would be worse. The current problem comes about because we cannot scale the Higgs corrections up to the Planck-scale where we know there is new physics. If we remove that scale then we have a theory which has no upper scale limit and so should generate infinitely large corrections to the Higgs mass i.e. we go from an incredibly unlikely 1 in ~10^34 chance of the corrections giving such a light Higgs to a zero percent chance of the theory giving a light Higgs, or any Higgs with a non-infinite mass.

Obviously, if this is the case, G has nothing to do with Fermi's constant and we should not compare the two.

You are getting your 'g's and 'G's confused. In the muon g-2 experiment the 'g' is the muon's anomalous magnetic dipole moment. This is a precision test of Quantum Electrodynamics. The high order corrections to this will involve Fermi's constant (G_F) due to W and Z loops but these contributions will be incredibly small and were this any other experiment I would have said negligible but perhaps not in this case given the incredibly high precision involved. Neither of these constants have anything to do with the gravitational constant (G) nor the local acceleration due to gravity (g). So we are not comparing the two.

It's the holy grail of modern pseudo-scientists: getting an angreement with a former major geek site, allowed to directly post articles. Sure, there are unanswered questions in it, ranging from dark matter to the hierarchy problem to the strong-CP problem, but still they swallow the clickbait until they find another method to squeeze the last remaining bit of income from this community. Or is there? Take a look at the evidence from user StartsWithABang, and see what might be the future of Slashdot.

Have you actually read through the discussion in here that was spawned by this article? It is like a sea of stars are shining. So much information, so much intelligent discussion... and we get to see it all. Absolutely amazing. You can not find the quality of discussion about this stuff anywhere else where normal humans congregate. I feel like my understanding of the universe and certainty of direction has been solidified by seeing all of this.

Could we flag this kind of articles with a warning, please? I'm getting tired of glossy gossip that's more suited for a write-up about soap-stars and Big Brother. Give us a hex-dump or a wall of equations to look at, not chatty nonsense trying to invoke a sense of "Woooh, mysterious!!!!"

No, I just want to see scientific fact presented as if it is scientific fact. Telling about science doesn't need to be pepped up - the subject is already exciting, as opposed to the disturbed love lives of Big Brother contestants, and people on/. are interested in "News for Nerds", or so I've heard. There was once, when a nature program on telly or a scienticif article would be exactly that: exciting facts about nature; compare David Attenborough standing waist deep in a swa